In this case, a conventional barrel weapon refers to a weapon, such as an artillery piece, naval gun, or tank cannon, that comprises a barrel from which a projectile is fired and propelled through the barrel by a propellant charge that is ignited using a pyrotechnic igniter, e.g. an ignition screw, ignition cartridge, etc. The propellant charge, also referred to as the propelling substance, refers here to gunpowder in solid form, and on ignition, it emits gases which, under high pressure inside the barrel, impel the projectile toward the muzzle of the barrel. The propellant charge may also be of a type other than solid gunpowder.
High gas pressure for long periods allows a high muzzle velocity to be achieved. High muzzle velocity of the projectile is used e.g. to increase the range of the weapon, improve the projectile's penetration capacity, or allow the projectile to complete its trajectory in shorter time.
A pressure curve for an optimal combustion process and thus a high firing rate should show an almost immediate pressure increase to Pmax, followed by a stable plateau phase with a constant barrel pressure maintained at Pmax through the entire time the propellant charge is burning inside the barrel, and should then immediately drop to zero when the projectile leaves the barrel. Ordinarily, all of the propellant charge should have been consumed at this point.
Regardless of which propellant charge is chosen, the ignition process is highly relevant to the course of pressure. A plasma generator having variable ignition energy makes it possible to induce instantaneous flashover ignition of the entire propellant charge and thus allows an immediate pressure increase. A plasma generator also provides the advantage that the ignition energy may be varied over time, which is not the case with a pyrotechnic igniter. Variable ignition energy means that the ignition energy can be adapted to various types and sizes of propellant charges in order to vary the range and also to compensate for the dependency of the propellant charge on temperature.
A parallel development for the purpose of increasing the firing rate of a weapon is to reduce the vulnerability of the propellant substance. Propellant substances of this type are referred to as having “low vulnerability,” in English LOVA (LOw VulnerAbility). Low-vulnerability propellant substances are difficult to ignite, which reduces the risk of unintentional ignition of the propellant substance in high-risk situations, e.g. when a combat vehicle comes under enemy fire. This reduced vulnerability also places increased demands on igniters. In such cases, the igniters must generate an increased amount of energy and/or increased pressure in order to bring about the ignition process. Igniters ordinarily contain a readily-ignited ignition substance, and if the amount of this ignition substance is increased, this runs completely counter to the use of a propellant charge of the LOVA type. In principle, ignition takes place by means of an ignition sequence, in which an extremely small amount of vulnerable ignition substance, referred to as the primary explosive, e.g. lead azide or silver azide, is ignited by a mechanical shock or an electrical pulse. The primary explosive then ignites the secondary explosive of the igniter, usually blasting powder. Replacing the pyrotechnic igniter or the entire ignition sequence with a plasma igniter reduces the vulnerability of the system to unintentional ignition. At the same time, this allows increased dynamics so as to generate the more powerful ignition pulse required to ignite low-vulnerability propellant substances (LOVA).
Conventional igniters also entail logistical or technical problems. For barrel weapons that use propellant charges separately from projectiles, such as artillery or larger calibre vehicle-mounted cannons, one often uses a separate ignition cartridge to ignite the propellant charge. One ignition cartridge is used for each firing. A mechanical system must therefore be mounted on the cannon for storage, charging, and removal of the ignition cartridges. By using a plasma igniter, one can avoid the logistical problems connected with the ignition cartridge. A commonly-occurring problem is that the ignition cartridge becomes jammed in the cartridge chamber. The ignition cartridge expands when the weapon system is fired, with the result that the cartridge is firmly wedged in the cartridge chamber, resulting in a misfire. The use of a plasma igniter allows misfiring to be avoided, thus increasing the weapon's functional safety.
Plasma igniters for igniting propellant charges are described e.g. in U.S. Pat. No. 5,231,242 (A) and U.S. Pat. No. 6,703,580 (B2). These plasma igniters are based on the principle of explosive wires, i.e., an electrically conductive wire that is heated, gasified, and partially ionized by an electrical current. The drawback is that the wire is consumed and must be replaced with a new one before each firing. Plasma igniters are therefore of the single-use type.
Repeatable plasma igniters are known in the art, e.g. in patent documents DE-103 35 890 (A1) and DE-40 28 411 (A1). These plasma igniters are based on the principle that an electrically conductive liquid is sprayed in between two electrodes having a potential difference at which the electrical circuit short-circuits and generates an electrical discharge that causes plasma generation. The use of liquids involves a complicated arrangement or easily-ignited substances. The use of liquids also requires complicated logistics for handling said liquids.